1. Field of the Invention
This invention relates to power transmission belts having a length and laterally spaced side surfaces, with a mark on one of the laterally spaced side surfaces. The invention is also directed to a method of providing the mark on the power transmission belt.
2. Background Art
It is conventional to provide a mark on the back side of a power transmission belt. The mark may convey a wide range of information, such as a company name, a trademark, a model number, date material, etc. In one conventional process, a transfer mark is formed consisting of unvulcanized colored rubber, or the like, which is applied to a base material that may be a transparent synthetic resin film. The film, with the transfer mark thereon, is then applied to a molding drum. The belt components are then sequentially built up upon the drum over the film with the transfer mark thereon. As one example, the components may be a rubberized canvas layer, a tension rubber layer, a load carrying cord, and a compression rubber layer. The components may form either a single belt or a larger width belt sleeve. The belt/belt sleeve is then fit with a jacket, after which vulcanization is carried out. At completion of vulcanization, the film is removed from the belt/belt sleeve, leaving the mark adhered to the rubberized canvas layer.
During the vulcanization process, the mark and the base material to which the mark is applied become pressed into the back side of the belt/belt sleeve. The back side of the belt/belt sleeve may become depressed in the region where the mark and base material are applied. As a result, the back side of the belt/belt sleeve may have one or more steps thereon so that the back side surface is not uniformly flat.
This condition becomes significant particularly with V-ribbed belts used for driving accessories on automobiles, and particularly those systems in which a V-ribbed belt is used to drive multiple shafts. In a typical arrangement, the belt is looped in a serpentine manner around various automobile engine components, with the back side of the belt engaged by a tensioner. An uneven surface on the back side of the belt might produce vibrations during operation. This vibration may lead to unwanted noise generation. Additionally, when this condition is present, the use of the back side to drive one or more components may cause noise generation in use.
Various alternative methods of applying a mark to a belt/belt sleeve are known. For example, in JP-B-7-96330, a method is disclosed in which a transfer mark assembly is used, consisting of a mark on a base material and a canvas including unvulcanized rubber which are placed in lapped relationship with the mark facing the canvas layer. After heating and pressurization, the base material is stripped off to transfer the mark to the canvas layer before the canvas layer is integrated into a belt.
In JP-A-8-152048, a mark is applied on a base material of non-woven fabric, which is applied on a covering canvas for a belt to integrate the mark into the covering canvas.
However, with the above described methods, the mark on the back side of the belt tends to be easily erased when the back side of the belt is used as a driving face in contact with a pulley. This erasure occurs as a result of repeated rubbing between the back side and a cooperating pulley. Accordingly, there is a tendency for the mark to become unreadable relatively soon after the belt is installed and operated. Thus, the information which is desirably legible for a significant portion of the belt life, such as the manufacturer's name, a trademark, month and year of manufacture, manufacturing lot number, etc. may be made illegible.
In JP-A-7-233992, a method is disclosed in which an ink jet printer is used for directly printing a mark on the back side of a belt without using any separate carrier/base material. According to this method, a mark is printed directly by injecting ink on the back side of the belt using an ink jet printer. According to this method, each of the belts is prepared by cutting the belt to a desired width from a belt sleeve. A number of the belts are arranged on a supporting table and secured thereto. The supporting table is then moved to a printing position at which the ink jet printer can be operated to apply the ink. The ink is injected from an ink head onto the belt to produce the desired mark.
Ink applied through an ink jet printer is also prone to being erased after rubbing occurs between the back side of the belt and a cooperating pulley system.